What kind of material for swimsuits is best?

By the way I meant competition/fitness swimsuits. Not bikinis or anything to go to the beach with.

I’ve been looking around for some swimsuits lately and I’m not quite so sure what type of material I should go for.
Two years ago when I swam competitively, I bought a Speedo swimsuit made of 100% polyester, its still in good condition, but its starting to stretch out due to daily wear.
Last year I bought a Nike (thin strap) one which is 92% polyester and 8% XLA/spandex and halfway through the season its already stretched out so much!
But this time, because of sales, I really wanted to get a swimsuit that would last me like the speedo one. Should I go for 100% polyester or mixed? I also heard nylon ones really….dont last at all.